Document the notify sound parameter for /chatbox/input

[z3y]

https://github.com/vrchat-community/osc/wiki/Chatbox /chatbox/input s b b the third parameter being a bool for chatbox notify sound

https://docs.vrchat.com/docs/vrchat-202241#features:~:text=The%20OSC%20endpoint%20/chatbox/input%20was%20updated%20to%20include%20an%20additional%20bool%20parameter%20for%20MessageComplete%20which%20is%20used%20to%20trigger%20the%20notification%20SFX